Process and sheet packaging material for inhibiting corrosion



I atent 2,75%,120 Patented July 24, 1956 fine PROCESS AND SHEETPACKAGING MATERIAL FOR INHIBITING CORROSION Robert L. Lothringer,Homewood, Ill., assignor to Sinclair Refining Company, New York, N. Y.,a corporation of Maine No Drawing. Application November 12, 1952, SerialNo. 320,131

6 Claims. (11. 21-25 My invention relates to corrosion inhibition andmore particularly to vapor phase corrosion inhibition in which theinhibiting agent vaporizes to deposit a protective coating on metalsurfaces.

Internal corrosion occurs in natural gas gathering lines and in naturaland water gas transmission mains and distribution lines, storage tanks,etc., because of traces of moisture inevitably present in the gas. Thiscorrosion is a major problem to the gas industry and has two mainaspects, i. e., replacement of corroded equipment and service calls toadjust and clean consumer appliances. combat internal corrosion of pipelines, the gas industry has resorted to oil fogging which consists ofinjecting an oil of low volatility as a fog into the gas stream in thelines to form a thin coating of oil on the metal surfaces. Thisexpedient is disadvantageous however because the oil fogs will not becarried for long distances, for exam ple, in the fingers of adistribution line, wherein flow rates are low enough to allow even thefinest fogs to settle, and the oil must be fogged into the gas stream atnumerous points throughout the system to obtain adequate protection.

In addition to the corrosion problems of the gas industry there are theproblems of transportation and storage of ferrous metals and ferrousmetal products such as sheet steel, iron pipe, petroleum productsstorage tanks, machine parts etc. These metal objects are usually quitesusceptible to the corrosive action of water vapor contained in theatmosphere. Where size permits it has been customary to wrap and sealthem in moisture-proof wrappers or packages but this is impracticable inmany cases. Even where practicable such precautions have not been whollysuccessful for despite the best efiorts corrosion still occurs sincesome water vapor is usually trapped in the wrapping or packaging when itis sealed, and additional moisture penetrates to the interior of thewrapping or packaging after it is sealed.

These and other problems are overcome according to my invention byproviding an atmosphere containing vaporized ammonium naphthenate incontact with the metal surfaces to be protected from which atmospherethe corrosion inhibiting vaporized ammonium naphthenate deposits on themetal surfaces as a protective film. When injected into gas pipe lines,the vaporized ammonium naphthenate is carried, for example, in the caseof natural gas, along with the gas stream from the gas field to theultimate consumer and eventually coats and protects the interiorsurfaces of all metal in the entire system whether it be in thegathering lines, storage vessels, transmission mains or in the manyfingers of distribution lines. Similarly the protective film depositedfrom an atmosphere containing vaporized ammonium naphthenate surroundingmetal objects to be protected makes absolute sealing of the metalobjects in moisture-proof wrapping or packaging unnecessary and negatesthe corrosive effect on the metal objects of the moisture trapped in thewrapping or packaging when it is sealed.

In one aspect of my invention an atmosphere containing vaporizedammonium naphthenate may be provided in gas gathering, storage,transmission and distribution equipment by fogging the ammoniumnaphthenate, preferably dissolved in a suitable solvent, directly intothe appropriate gas pipe line. Either cold fogging, which consists ofatomizing the inhibitor by a gas jet into the gas stream, or hotfogging, which consists of bubbling the gas through hot inhibitorcontained in an externally heated tank, may be employed. I prefer thecold fogging procedure since I have found that there is some possibilityof decomposition or at least darkening of the inhibitor from hightemperature storage. Similarly an atmosphere containing vaporizedammonium naphthenate may be provided in closed containers bydistribution in the liquid state.

The total amount of ammonium naphthenate required for gas lineprotection will vary with conditions such as the average linetemperature, the amount of moisture present, and the amounts of pro-rustimpurities. The quantity'of inhibitor required to be adsorbed oninterior surfaces of the pipe will also vary depending on the pipecondition. For example, tests indicate that a monomolecular film wouldbe adequate on clean steel. Pipes coated with a heavy rust layer,however, will require enough inhibitor to coat both the rust and thesteel surface before corrosion is arrested. Inhibitor use at a highconcentration followed by concentration reduction to a minimum amount istherefore recommended. Initial dosage may go as high as 10 pounds ofammonium naphthenate per million cubic feet of gas but after theinterior pipe surfaces have been coated protection might be maintainedusing at little as 0.01 pound per million cubic feet.

In another aspect of my invention an atmosphere containing vaporizedammonium naphthenate is provided by vaporization of the inhibitor from acoating or impregnating composition applied to a wrapping or packagingmaterial on the surface to be placed adjacent the metal surfaces. Thecoating or impregnating composition may consist essentially ofammoniumnaphthenate although materials such as, for example, urea and sodiumbicarbonate may be added for pH control where required. The wrapping orpackaging material advantageously is a fibrous material such as paper,cardboard, textile, wood, fibreboard, etc. With particular advantage,the wrapping or packaging material comprises a laminated fibrousmaterial, for example, a crepe style kraft paper stock, the

laminar sections of which are laminated together by means of a fl xiblemoisture resistant laminant for example, asphalt, resinous typelaminants, etc. The surface of the wrapping or packaging material to beplaced adjacent the metal surface is coated or impregnated with ammoniumnaphthenate. The coating or impregnating composition may also consistessentially of a hydrocarbon vehicle and. ammonium naphthenate. Thehydrocarbon vehicle must be inert, capable of forming a dispersion orsolution of the ammonium naphthenate and capable of being applied to apackaging material. For example, the vehicle may be an oil of a suitableviscosity and flash point such as a kerosene, a gas oil cut, or alubricating oil fraction. For example, desired concentrations ofammonium naphthenate may be dispersed in a bright stock or a neutral, e.g., a conventionally refined neutral of about SSU at F. The vehicle maycomprise a wax such as a paraflin wax, a petrolatum or amicrocrystalline wax, or a bituminous product such as an asphalt. Thecomposition is applied as a coating to the wrapping or packagingmaterial by an suitable means.

I The actual amount of inhibitor employed in coating compositions isordinarily directly related to the amount of sealing of the wrapping orpackaging material, the type of metal to be protected, the degree ofexposure to'which the packaged metal will be subjected, and the periodof time during which it is to be protected. enclosed or open airtransportation or storage with constantly varying temperature andhumidity are capable of affecting corrosion considerably. A coatingcomposition containing ammonium naphthenate applied to a packagingmaterial carrier should contain in general ammonium naphthenate inamounts of about A to grams and preferably 1 to 2 grams per square footof treated carrier. Froman economic viewpoint, it is generallyunnecessary to use more than about per cent by weight of ammoniumnaphthenate in the coating composition.

Ammonium naphthenate is a material the preparation of which isconventional. The commercial product generally is produced by addingammonia to a mixture of naphthenic acids with acid numbers from about180 to .300. Such acids are described in the literature as being.carboxylic acids containing a cyclopentane nucleus. I have found thatammonium naphthenates made from mixtures of acids having acid numbers of230 and 260 have particular utility as vapor phase corrosion inhibitingagents. Ammonium naphthenates are generally in the form of a liquid or asoft gel. For purposes of injection into gas lines, however, they may beadmixed witha suitable diluent such as kerosene to achieve a desiredviscosity.

A corrosion test apparatus was designed to simulate gas pipe lines fortesting the effectiveness of ammonium naphthenate as a vapor phasecorrosion inhibitor. The apparatus included a unit containing oil wellbrine, a unit containing cotton, a first test chamber, a unit containingammonium naphthenate, a second test chamber, a vacuum trap and a causticabsorber. The outlet end of the apparatus was attached to a vacuum lineand a mixture of air and hydrogen sulfide was drawn slowly through theapparatus at a pressure of approximately 10 centimeters of mercury. Thegas mixture was saturated with moisture in the brine containing unit andany moisture drops present were absorbed in the cotton containingunitprior to passage of the saturated gas mixture to thefirst testchamber. This test chamber contained a small metal test coupon whichcould be removed at time intervals for determining weight loss. Thesaturated gas mixture then passed through the inhibitor containing unit,a second test chamber identical with the first containing a similarremovable test coupon, the vacuum trap, and the caustic absorber forremoval of hydrogen sulfide and inhibitor before passage into the vacuumline.

Ammonium naphthenate dissolved in 50 per cent PD kerosene was tested inthe apparatus for 21 days. The test coupon in the first test chamberweighed 24.1000 grams prior to the test and 24.0728 grams after cleaningat the end of the test, a 0.0272 gram loss in weight representing 0 percent corrosion protection. The test coupon from the second test chamber,on the other hand, which was exposed to ammonium naphthenate, weighed24.0860 grams prior to the test and 24.0850 grams after cleaning at theend of the test, a 0.0010 gram loss in weight representing 97 per centprotection.

In additional tests, samples of ammonium naphthenate, ammoniumnaphthenate containing compounds, and kraft papers coated with ammoniumnaphthenate and such compounds were tested for vapor phase corrosioninhibitor properties. The various samples tested were prepared in thefollowing mannen,

Sample A A 440 gram portion of a commercial naphthenic acid with an acidnumber of 230 was partially neutralized to 72 per cent of the acidnumber with 2000 cc. of 2 per cent sodium hydroxide solution. Thismixture was extracted with 500 cc. of pentane to remove unreacted acidsand inert materials. The remaining soap solution was then acidified withsulfuric acid and was allowed to stand In particular,

until an acid and a water layer formed. The water layer was drawn oiiand discarded. The acid layer was washed three times with 1000 cc.portions of water and the remaining acid weighed 250 grams whichrepresented a 57 per cent yield. The purified acid was neutralized witha slight excess of ammonium hydroxide solution after which the mixturewas heated until excess water and ammonia were removed.

Sample B A 100 gram portion of a commercial naphthenic acid with an acidnumber of 230 was heated and mixed with 20 grams of charcoal. Thecharcoal was removed by filtration while the mixture was still warm. Thetreated acid, which was much lighter in color, was heated to 150 F. andanhydrous ammonia was bubbled through the vigorously stirred acid untilthe solution was neutral to litmus paper. The neutralized acid was thenmixed with urea and sodium bicarbonate to give a mixture containing byweight per cent ammonium naphthenate, 10 per cent urea and 5 per centsodium hydrogen carbonate.

Sample C A kraft paper was coated by dipping the paper into a portion ofSample B and removing the excess with a piece of cloth.

Sample D stirred vigorously while anhydrous ammonia was bubbled throughthe solution for one hour. The reaction product was tested with litmuspaper and it indicated a neutral soap. Four drops of mask odor was addedfor odor improvement.

Sample E A portion of Sample D was applied to a kraft paper using aconventional paper coating machine. The coating machine passed the paperthrough the inhibitor at 150 F., over a metering rod, and then over tworolls at 212 F. The hot rolls served to force the material into thepaper. 14.4 pounds per ream or 2.3 grams per square foot.

The various samples were tested for vapor phase corrosion inhibitionproperties using the following procedure. A 200 milligram portion of theinhibitor or inhibitor containing compound was coated on the walls of a4 ounce bottle, or a 2 inch by 2 inch strip of butcher paper coated with60 milligrams of the inhibitor or inhibitor containing compound wasplaced therein. A freshly polished mild steel strip was suspended withinthe bottle from a hook attached to a cap andthe cap was screwed tightlyinto place. The assembly was then placed in an oven at F. for twenty-twohours to allow the inhibitor to precoat the test strip. At the end ofthe precoat period the bottle was removed from the oven and placedin anice box at 40 F. for an additional two hours. Five milliliters ofdistilled water was then added and the bottle replaced in the oven fortwentyfour hours after which the test strip was removed, dried and ratedas follows:

A, Perfect.

13+ Less than A of total surface covered with rust. 13+, to 5% of totalsurface covered with rust.

B, 5% to 25% rust.

C, 25% to 50% rust.

D, 50% to 75% rust.

E, Over 75% rust.-

The results of these additional tests using the 4 ounce bottle testdescribed above are indicated in the data given below. It should benoted, however, that the tests were conducted under extreme conditionsof temperature and The compound was meter on the paper at humidity. Incommercial use of my inhibitor these conditions are not likely to exist.

Sample Rust Test Results 1 a 85%, Medium to Heavy Rust.

13+, B+, 1% light rust. B+, 1% light rust.

B+, B+, %%light rust. B+, 13+, light rust.

1 Number of results indicate number of tests.

I claim:

1. A method of inhibiting corrosion of enclosed ferrous metal surfaceswhich comprises maintaining an atmosphere containing vaporized ammoniumnaphthenate in contact with the metal surfaces in amounts such that atleast 0.1 pound of ammonium naphthenate is present for each millioncubic feet of enclosed space.

2. A method of inhibiting internal corrosion of ferrous metal surfacesof gas gathering, storage, transmission and distribution equipment whichcomprises injecting into the gas stream flowing in such equipment from0.1 to 10 pounds of ammonium naphthenate per million cubic feet of gas.

3. An article of manufacture which is useful in the packaging of metalobjects in order to prevent their corrosion, said article being a sheetpackaging material to which has been applied in amounts of about 0.5 to5 grams per square foot of material a vapor phase corrosion inhibitingcomposition consisting essentially of ammonium naphthenate.

, 4. An article of manufacture which is useful in the 6 packaging ofmetal objects in order to prevent their corrosion, said article beingpaper to which has been applied in amounts of about 1 to 2 grams persquare foot of paper a vapor phase corrosion inhibiting compositionconsisting essentially of ammonium naphthenate.

5. An article of manufacture which is useful in the packaging of metalobjects in order to prevent their corrosion, said article being amaterial to which has been applied a vapor phase corrosion inhibitingcomposition consisting essentially of a hydrocarbon vehicle and ammoniumnaphthenate, the ammonium naphthenate being present on the coatedmaterial in amounts of about 0.5 to 5 grams per square foot.

6. An article of manufacture which is useful in the packaging of metalobjects in order to prevent their corrosion, said article being paper towhich has been applied a vapor phase corrosion inhibiting compositionconsisting essentially of a petroleum wax and ammonium naphthenate, theammonium naphthenate being present on the coated paper in amounts ofabout 1 to 2 grams per square foot.

References Cited in the file of this patent UNITED STATES PATENTS2,185,954 Ryner Jan. 2, 1940 2,587,249 Ulmer Feb. 26, 1952 2,629,649Wachter Feb. 24, 1953 2,643,176 Wachter June 23, 1953 OTHER REFERENCESInd. and Eng. Chemistry for December 1948, pages 2338 to 2347.

1. A METHOD OF INHIBITING CORROSION OF ENCLOSED FERROUS METAL SURFACESWHICH COMPRISES MAINTAINING AN ATMOSPHERE CONTAINING VAPORIZED AMMONIUMNAPHTHENATE IN CONTACT WITH THE METAL SURFACES IN AMOUNTS SUCH THAT ATLEAST 0.1 POUNDS OF AMMONIUM NAPHTHENATE IS PRESENT FOR EACH MILLIONCUBIC FEET OF ENCLOSED SPACE.